The proposed research will attempt to demonstrate that organo-cobalt complexes, relevant to the B12 coenzymes, undergo equatorial ligand proton dissociation in aqueous base to form activated complexes with considerable carbanion-like character on the carbon bound to cobalt. A conclusive demonstration will be made that such activated organo-cobalt complexes readily undergo attack by relatively weak electrophiles, especially disulfides. This work will provide a model system for enzymatically mediated cobalt-to-sulfur methyl transfer known to occur in methionine and methane synthesis. The principal objectives include 1) a conclusive demonstration of base-catalyzed electrophilic cleavage of organocobalt complexes by disulfides, 2) determination of the stereochemical course of this reaction and 3) a kinetic study to determine the sensitivity of this group transfer reaction to the electrophilicity of the disulfide reactant. Alkylcobalamins and cobinamides will be utilized in this work as well as alkylcobaloximes. The major techniques to be used include uv-visible and proton nmr spectroscopy as well as gas chromatography and mass spectrometry.